The present invention relates to a drum brake shoe and more particularly to a drum brake shoe having a noise dampener.
The application of brakes to slow or stop a vehicle causes significant amount of noise to emanate from the vehicle. Such noise originates from the interface between the brake drum and a friction material during braking. Resonance develops at the friction material brake drum/rotor interface which may be transmitted through the brake shoe assembly, the mounting hardware and suspension system thereby causing objectionable noise to emanate from the vehicle.
The prior art has recognized the problem of noise generated during braking. Therefore, significant effort has been made to reducing objectionable noise generated in a drum brake assembly. For example, as shown in FIG. 1, a mass dampener 1 is positioned directly on the inner periphery of the arcuate brake show 2. Further efforts, as depicted in FIG. 2, have been directed to providing a plurality of reinforcements 3 arranged at irregular intervals on each side of the web plate 4 thereby increasing the torsional rigidity to inhibit resonant vibrations.
Unfortunately the prior art fails to provide an adequate and definite solution to the noise problem. Large vehicles such as trucks and busses are particularly susceptible to the generation of noise during the braking process and the aforementioned attempts to reduce the resonance and noise emanating from the brake drum friction material interface have been least successful in these applications.
When the lining contacts the drum, the lining does not smoothly apply itself to the drum surface. During braking there is a stick slip motion that has a definite frequency for every lining formula, drum material and operating temperature. Every lining has temperature windows that produce noise. Every system (suspension, springs, axles, drum, tires, rims, etc.) has a frequency that produces noise. Because noise and wear dynamically relate to one another, designers have difficulty finding a compromise to reduce noise for a given application. Therefore, it is desirable to dampen or counter act the frequency of the stick slip of the lining to the drum at the source. Such dampening would allow brake designers to concentrate on longer wearing linings with less consideration given to noise.
It is an object of the invention to provide an improved brake shoe that reduces noise by damping or countering the frequency of the stick/slip between the brake shoe and drum surface and overcomes the drawbacks of and improves upon the related art.
The present invention is directed to brake shoe having a noise dampener made of a yielding member secured to the web plate. The yielding member is provided to dampen or counter stick/slip frequencies resulting from the interaction between the brake drum surface and the brake lining during a braking event. Preferably the brake shoe includes two spaced-apart web plates and the yielding member is a coiled spring disposed there between.